<wicket:extend xmlns:wicket="http://www.w3.org/1999/xhtml">
    <div wicket:id="filter">
        <label wicket:id="classLabel"></label>
        <div wicket:id="classes"></div>
        <label wicket:id="documentLabel"></label>
        <div wicket:id="documents"></div>
    </div>
</wicket:extend>